Comments by "Javier Flores" (@JJFlores197) on "What is a SWITCH? // FREE CCNA // Day 1" video.

  1. The computers are connected to each other via a switch. When you send a ping from 1 PC to the other, the PC sends the entire IP packet, but the switch only understands MAC addresses. it doesn't matter since the switch only cares about the MAC addresses which it uses to deliver the frame to the correct device. The network stack of the computers allow it to receive the packet and then respond to the ping (assuming no firewall rules are in place preventing this).
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  2. Nope. The current state of the videos is far from complete. NWC is a good presenter, but he still has a very, very long way to go to finish the series. The videos are good if you want a high level overview of networking, but none of them go in-depth as they should to be called "CCNA". He hasn't even shown you how to configure a Cisco router or switch. I suggest watching Jeremy's IT lab and/or David Bombal. They may not be as "exciting" and "energetic" as NWC, but they are much more informative and complete.
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  3. No. I believe they are technically layer 1 devices since a hub pretty much sends all data from its ports to every port. As such, it has no concept of any of the higher layers of the OSI model. I wouldn't really worry about hubs. They are practically useless in most applications nowadays.
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  4. With the current state, its a limited high level overview. I would use other channels like David Bombal or Jeremeys' IT Lab. They may not be as "fun" or exciting as NWC, but they are complete and much more informative.
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  5. Yes the switch doesn't understand IP addresses. The computer uses a protocol called ARP -Address Resolution Protocol. In short, ARP maps IP addresses to MAC addresses. So when you ping a computer, your PC sends out an ARP packet. It basically asks in the network, what is the MAC address of this IP address? All devices on the network receive this since its a broadcast frame. however, all devices except the intended recipient will discard the broadcast frame since its not meant for them. The intended device will respond back to your PC with its MAC address. At this stage, the PC will remember that MAC and IP address and create an entry in its ARP cache. After that, the PC will send a packet with the destination IP address. Inside of this packet, is a frame which now contains the other PC's MAC address. The switch receives this packet, but it discards the layer 3 header, since again, it doesn't understand IP address. It only cares about the layer 2 header which contains the source and destination MAC addresses. It will then forward the frame to the intended destination.
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  6. He doesn't. At least not initially. In order to send a computer an IP packet, your PC (source) needs to know both the MAC and IP addresses. But if it doesn't know the MAC address, what will happen is that the PC sends a broadcast frame. This is a frame that is sent to all connected devices (hence the term broadcast) on that switch. It basically asks "What is the MAC address of the device with x IP address?" All devices on that switch receive this broadcast, but they all ignore it except the intended recipient. It responds back to Mark's PC with its MAC address. Then, Mark remembers this MAC address in his ARP cache. From that point, Mark's PC can send Lisa's PCs data since it now has both IP and MAC addresses.
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  7. And you're following exactly the steps he's showing? Its hard to troubleshoot these issues without any details.
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  8. You'll want to use other resources as well. This video series is very far from being complete. There is still a lot of information he hasn't covered.
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  9. The exam costs $300... not cheap. I would suggest using other sources to study. Network Chuck is a good presenter, but this video series is extremely incomplete. I suggest watching Jeremy's IT Lab. He's not as entertaining as NWC, but his training series is actually complete.
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  10. Well no, but its preferred to use an ethernet cable where it makes most sense.
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  11. He goes over it in the next video. In short, there's something called an ARP Broadcast that is sent out. ARP - Address Resolution protocol maps MAC addresses to IP addresses. Mark needs both the MAC and IP address of Lisa's computer to send a message. Since it only has the IP address, Mark's PC sends a broadcast frame. This broadcast basically asks, "What is the MAC address of x IP address?" The broadcast frame arrives at the switch. The switch sees that it is a broadcast and as the name implies, it broadcasts it to all the devices connected to that switch. All devices will ignore the broadcast frame except for Lisa's computer. Lisa will respond to Mark with her MAC address. Once Mark's computer receives it, it will store it in its ARP table. Then, Mark's PC can ping Lisa's computer.
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  12. Its the "N" key. Its to add a comment, so you have to manually type it out.
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  13. Nope. What you're referring to is a broadcast frame. This only happens when a device on the network wants to know the IP address of another device. So let's say you have a network of 5 PCs (PC's 1 -5) and 2 phones. If PC 5 wants to know the IP address of cell phone 1, it (PC-5) will send a broadcast message asking what the IP address of the phone is. The switch will see this broadcast frame and send it to all other devices connected to it. however, all devices except for cell phone 1 will ignore the broadcast frame. Cell phone 1 will respond to PC-5 with its (cell phone 1) IP address. When you get a WhatsApp message, it arrives at the router. The router then figures out what device it is intended for and only sends it to that device.
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  14. I think he added a label. I believe that the shortcut is either the k or m key, but don't remember.
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  15. Its called a broadcast frame. When your PC wants to talk to another PC in your network, it needs the recipient PC's IP and MAC address. Your PC already has the IP address, but now it needs the MAC. Your PC will send a broadcast frame. The switch receives this frame and then sends it to all devices connected to it. All devices except for the intended recipient will ignore it. The recipient PC will respond to your PC with its MAC address.
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  16. He goes over that in the next few videos. In short, there's a protocol called ARP. It maps MAC addresses to IP addresses. Say you have a network of 5 PC's: PC-1 - PC-5. PC-1 wants to send a ping to PC-5. PC-1 doesn't know 5's MAC address. So what 1 will do is send a broadcast frame. This is basically a frame that asks "What is the MAC address of the device with x IP address?". The switch receives this frame and sends it to all switch ports. All of the computers on the network, except for the intended recipient ignore the frame. PC-5 responds to PC-1's broadcast frame and it will send its MAC address. PC-1 learns PC-5's MAC address and stores it in its ARP cache. After this point, PC-1 can send a frame to PC-5 with the correct IP and MAC address information.
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  17. The switch has a CAM table with a list of what MAC address is associated with what physical port.
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  18. Let's say you have PC-1 and PC-3. PC-1 wants to send PC-3 a packet. In the frame, PC-1 adds the MAC address of FF:FF:FF:FF:FF:FF; this is a broadcast frame. The switch sees this frame and broadcasts it to every port on the switch, except the port it came from. All of the PCs see this frame but ignore it except for PC-3. PC-3 responds to PC-1 with its (PC-3) MAC address and then PC-1 receives it. PC-1 now knows PC-3's MAC address and can then send frames to it.
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  19. Well the switch only understands MAC addresses. The switch has a CAM table where it learns the MAC address of each device that is plugged into each of its ports.
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  20. The packet still contains the destination mac address - Lisa's computer. When it reaches the switch, it will send it to the correct device. Once Lisa's PC receives it, it will look at the frame (L2) and the packet (L3).
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  21. He adds a note. In the 2nd tool bar (from top to bottom), look for the notepad icon (right on top of Physical). Then you can create a note anywhere inside of the logical view.
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  22. so what exactly are you having trouble with? If you try to open the PKZ file in Packet Tracer, what happens? Need more details.
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  23. The CCNA is a more advanced and in-depth version of the Net+. The Net+ more or less just gives you the network fundamentals. CCNA takes those fundamentals and builds on it for Cisco-specific products. In your case, it probably won't be of much benefit unless you plan on working on cisco equipment. And this course is far from complete. There's still too many topics missing which is important for the CCNA exam.
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  24. Yes. I believe most Cisco switches have something called SPAN/RSPAN. It stands for Switched Port Analyzer. It allows you to mirror the traffic of a port over to another port sot hat you can capture it. Its typically done for diagnosing problems. In theory, you could use it maliciously, but it doesn't mean you'll get exactly what you want. Even if you are mirroring a port, all the data is still the same as the original port. In other words, if you have a client device that is communicating over https to a website, for instance, that data will still be encrypted even if you capture it via the mirror.
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  25. The thing is that the switch doesn't understand IP addresses, but it knows the MAC address of the computers and which switch port they are on.. There's a protocol called ARP that maps IP addresses and MAC addresses.
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  26. The packet still contains the destination mac address - Lisa's computer. When it reaches the switch, it will send it to the correct device. Once Lisa's PC receives it, it will look at the frame (L2) and the packet (L3).
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  27. Just a word of caution. his videos are entertaining, but they're not complete. If you're wanting to use his series to get your CCNA, I suggest watching other channels. NWC is a good presenter, but his CCNA series is extremely incomplete. There's still a ton of information (and I do mean a lot) he hasn't covered which is important to know for the CCNA.
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  28.  @sharpears1756  Jeremy's IT Lab is a good channel. He may not be as enthusiastic as NWC, but he has a complete CCNA series.
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  29. Are you able to login with your credentials in the packet tracer program?
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  30.  @DogmaOfHell  I'm honestly not sure. You may need to contact Cisco Netacad/SkillsForAll for help.
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  31. You don't. At least not unless you buy a used router or switch on eBay or other website that sells network hardware. I bought a $100 Cisco 1941 router several years ago to play around with. The only downside is you can't get software updates without an active service contract with Cisco which is expensive.
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  32. You have to scroll across....
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  33. Hate to burst your bubble, but there's a lot of information that's missing for a "CCNA" course. He's a good presenter, but he still has a very long ways to go to make a complete series.
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  34. It doesn't look like there's any special network configuration on the switch in the packet tracer file. You have to make sure you manually assign the host devices IP addresses.
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  35. What exactly do you need help with?
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  36. Yes. I'm sure you totally make huge profits since you started trading with a professional broker and used her top notch trading strategy...
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  37. I think he goes over in the next video. In short, when the 1st PC sends data to the 2nd PC, PC 1 adds the MAC address of the 2nd device in the destination MAC address. However, if PC1 doesn't know PC2's MAC address, PC1 first sends a broadcast frame. Basically a broadcast frame is a message that's sent to all devices on the network. The broadcast frame basically asks "What is the MAC address of the device with this IP address?". Since its a broadcast, all devices on the network receive it, but all devices will ignore that frame except for the intended device. PC2 will then respond to PC 1 with its (PC2) MAC address. From that point, PC1 will add PC2's MAC address in the destination mac address whenever it sends it data.
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  38. Its not a good idea to that for security reasons. Also, most ISPs will only give you 1 public IPv4 address so that means only 1 device will be able to go online. That's why you need a router of some sort.
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  39. Your PC will send both the IP and MAC addresses in the data packet. So when it goes from your PC to the switch, the switch only looks at the layer 2 header which contains the source and destination MAC addresses. It will then forward the message to the intended MAC address and switch port.
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  40. The broadcast frame that is sent from the PC contains the destination MAC address of FF:FF:FF:FF:FF:FF The switch receives this frame and sees that MAC address. It knows to broadcast (hence the name) that frame out to all the other network ports.
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  41. Translating isn't exactly the correct word. There is something called ARP, Address Resolution Protocol. It essentially maps MAC addresses to IP addresses. In other words, when PC 1 pings PC 2, it (PC1) needs to know PC2's MAc address. Since it doesn't know it, it sends an ARP request. The switch receives this request and broadcasts it. PC 2 responds with its MAC address and then PC 1 learns it and stores it in its cache. The switch does something similar, but it uses a CAM table to keep track of what ports have which MAC addresses.
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  42. If you watch the 3rd video, it will make some more sense. There's something called ARP (address resolution protocol). It basically maps IP addresses and MAC addresses. When you ping from PC1 to PC2, PC1 doesn't know PC2's MAC address. It (PC1) sends a broadcast which the switch receives. Basically this broadcasts is asking "What is the MAC address of the device with the IP address of x.x.x.x?". The switch sends this frame to all devices plugged into it, but only PC2 will respond back with its IP address. PC1 now knows the MAC address and will store it in its ARP cache. It is true that layer 2 switches don't work with IP addresses, however, you have to keep in mind the OSI model. If you want to see this in action through Packet Tracer, look at the simulation tab. You can setup 2 PCs and a switch, connect them together, run the simulation mode and send a ping from one PC to the other and you'll get a visual of what's going on.
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  43. When you send a ping, your computer creates an IP packet and a data frame. The data frame contains the MAC address of your PC (source) and the destination PC. When the data frame reaches the switch, it only cares about the MAC address.
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  44. There should be a label/text button somewhere in the toolbar.
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  45. What does that even mean? "Put thru winzip???
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  46. He mentions it at 3:20. Its a PacketTracer file and the download is in the description.
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  47.  @rjaph842  What happens when you click on the link?
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  48.  @rjaph842  I'm not sure if my comments are shadow banned. Anyways, what happens if you clik on the l1nk for the packet tracer file
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  49. It only "acts" as a hub when a broadcast frame is sent.
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  50. What do you mean? You create a Netacad account and enroll in the Packet Tracer course and then download it.
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  51. You have to scroll to the right.
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  52. Good luck. I strongly suggest other resources. NWC's "CCNA" series is extremely incomplete.
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  53.  @kingofapirate  CCNA is a good certificate if you want to get into Cisco networking. You'll need to look at the price for your country. The Net+ is also decent, but doesn't hold as much weight as the CCNA.
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  54. The device manufacturer assigns a MAC address to device's network adapter at the time the device is built.
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  55. Nope. The MAC address is a layer 2 concept of the OSI model.
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  56. I suggest using videos from David Bombal and/or Jeremy's IT lab. NWC is a good presenter, but his video series, as-is, is very far from being complete. Your CCNA course will go much more in-depth than NWC's current videos. He hasn't even gone over how to setup a Cisco router and a switch, which is kind of important if you're studying for CCNA. He hasn't really gone over any of the Cisco-specific stuff nor many other important network concepts.
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  57. The switch is a layer 2 device and doesn't understand what an IP address is. There are layer 3 switches that can deal with IP routing, but that's a different story. Say you have a small network of 5 PCs - PC-1 - PC-5. Each has its own IP address assigned and you want PC-1 to ping PC-4. When you ping, PC-1, first sends an ARP broadcast message. This message basically asks what the MAC address of x IP address is. In this case, it is asking for PC-4's MAC address. The broadcast message arrives at the switch. As I mentioned, the layer 2 switch doesn't understand IP addresses, but it looks at the destination MAC address. Broadcast frames are FF-FF-FF-FF-FF-FF. This tells the switch to forward that frame to all ports. So PC-2,PC-3, PC-4, and PC-5 all receive that broadcast frame. All computers except for PC-4 drop this broadcast. PC-4 responds to PC--1 with its MAC address. PC-1 learns this MAC address and can then send the ping message to PC-4.
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  58. Your PC sends a broadcast frame. This frame is received by the switch and then resent to the other devices connected to the switch. All devices instead of the intended recipient will ignore the frame. When the intended recipient gets the frame, it will then respond back to your PC with its IP address. Your PC learns the MAC address it its ARP table (MAC address to IP address mapping). Switches do not understand IP address (unless we're talking about layer 3 switches, but that's a different topic).
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  59. I believe in a way, APs do work similar to hubs, but there is more complexity going on.
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  60. When you plug in a network device into a switch, the switch learns that device's MAC address and records it in the CAM table. Layer 2 switches have no concepts of ARP broadcast messages. They just work with data frames and MAC addresses.
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  61. What part of the video are you asking about?
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  62. Ping is a layer 3 concept. You can't "ping" a MAC addresses in that sense. Pinging works even without a router In this scenario because the computer systems have the software built-in (network stack) to deal with the OSI layers.
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  63. There is no ChromeOS (at least that I'm aware of) version of PT. You should be able to enable Linux apps on your CB and install the Ubuntu version of it.
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  64. Did you try scrolling to the right?
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  65.  @subhajitmondalr-4728  If you open Packet Tracer by itself, without any file, does it open fine?
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  66. I just downloaded it just fine....
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  67. Most non-tech savvy people don't care about hardwiring a device to the network. A lot of people prefer the convenience of wireless especially now that many have mobile devices and tablets. I also know there are many people who abhor seeing any type of wiring.
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  68. MAC addresses use a much larger address space than IPv4 addresses. MAC addresses use 48 bits instead of 32-bits that IPv4 addresses use.
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  69. I can see the pictures just fine in the file. You may need to redownload the file. Also, make sure your PacketTracer program is updated.
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  70. If you're talking about 16:07, then he used a note. You can see on top of the word "Physical", a clipboard looking icon. Click on that and you can add notes.
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  71. The IP addresses are pre-configured. You don't have to worry about this until later.
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  72. Its called a note. Press "K" or click on the note icon (above the Physical view button) to add a note.
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  73. What specific part of the video are you asking about?
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  74. Not in the slightest. Its a bit misleading as he claims its CCNA, but it lacks a lot of information. He's a good presenter, but this series is very far from being complete. There are many topics he hasn't covered, or if he did, it was brief and not at the level of detail it should be. Things like ACLs (access control lists), routing, switching, VLANs, and many more are missing. There isn't much Cisco-specific stuff he covers. Most of it is general networking knowledge which is fine, but it needs to also focus on the Cisco stuff.
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  75. It doesn't. Switches are layer 2 devices meaning they only understand MAC addresses. IP addresses are layer 3 concepts which most switches cannot comprehend (there are layer 3 switches, but for specific purposes, but that's a different topic). In order for a PC-A to talk to PC-B, A needs to know B's MAC address. If A doesn't know it, it will send a broadcast frame. That means that in the layer 2 frame, the destination is all "F"s. The switch receives this broadcast frame and will send it to all interfaces except the one it came from. The frame basically says "what is the MAC address of the device with this IP address: ?" All devices connected to the switch will receive this frame, but will discard it since it is not intended for them. However, PC-B will look at the frame and respond to it with its MAC address. The switch forwards this frame to the interface in which PC-A is plugged into and that is how PC-A will learn PC-B's MAC address.
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  76. eh... NWC is a good presenter, but he lacks depth. Most of his videos just get you the basic information. Its ok if just want to learn basic networking, but when you want to go deeper into how things actually work, that's where he doesn't do anything deeper.
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  77. What do you mean? The link for the lab file is in the description.
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  78. What tablet are you trying to ping? I don't believe there are any tablets in the PT file he shared.
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  79. Well the switch will learn the new device's MAC address and it to its CAM table.
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  80. The switch doesn't figure out anything based on IP address. Switches are layer 2 meaning they only work with data frames and MAC addresses. The PC sends a broadcast frame. When the switch receives this frame, it broadcasts (hence the name), the frame to all ports on the switch. All devices on the switch receive this frame but they all ignore it except for the intended recipient. That PC then responds to the sender PC with its MAC address. The sender PC then learns this MAC address and can now send data directly to that other PC.
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  81. I think he added a comment. I don't remember the shortcut though. you can find it by hovering your mouse over the icons and waiting for the little text to indicate what that button does until you find it.
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  82. You typed in the command incorrectly. It should be show mac-address-table
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  83. What do you mean??
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  84. Should be somewhere in the program settings. I don't recall the exact settings, but its in there.
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  85. Mikrotik is a company that makes routers and switches and other network equipment.
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  86. So what do you see?
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  87. I believe he added a note. Pressing the "n" key should let you add a note.
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  88. That is correct. Switches are layer 2 devices that work with frames and MAC addresses. Now there are some Layer 3 switches out there, but I don't know how common they are.
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  89. You're better off watching Cisco switch file management videos for specific information.
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  90. Click on the PC icon and then the "Desktop tab". Click on command prompt.
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  91. What do you mean?
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  92. The switch itself doesn't tell the computer the MAC address of the other devices. The switch's CAM table is just use for its internal use.
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  93. You may want to watch the next videos. He goes over that.
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  94. There's a scroll bar at the bottom. Scroll to the right to see the rest of the network setup.
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  95. You need more practice and better videos. I'm not saying Network Chuck's videos are bad. They're quite good and entertaining. However, his video series is very far from complete. There's still a lot of information (and I do mean a lot) that he hasn't covered. He hasn't even shown you how to configure a Cisco router and a switch! That's kind of important to know how to do... He's a great presenter, but he still needs a ton of work to get this anywhere close to being a "complete" training series. I recommend Jeremy's IT Lab CCNA course on YouTube. He may not be as enthusiastic as NWC, but his series is pretty good and actually complete.
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  96. If the switch interface is slower than the internet connection, then yes it will affect the speed. In most typical networks, there are 3 main speeds: 10 Mbps, 100, Mbps, and 1,000 Mbps (1 Gbps). If you have a 50 Mbps internet connection, but have a 10 Mbps switch, then you will get up to 10Mbps regardless of your internet connection speed or your computer's speed. Most, if not all consumer level routers and switches and the small business equipment support gigabit speeds so this will likely not be a problem unless you have an internet connection faster than a gigabit. There are enterprise level switches that support insanely fast speeds like 100Gbps.
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  97. Switches are used to physically connect devices in a network. For wireless networking, you need a wifi access point. In typical home/small business networks, the router acts as a router, network switch and wifi access point in one unit. In larger networks, you typically have dedicated wifi access points installed throughout the work area as needed to provide wifi connectivity. Those APs connect to a network switch with an ethernet cable.
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  98. The switch is a layer 2 device and doesn't understand what an IP address is. There are layer 3 switches that can deal with IP routing, but that's a different story. Say you have a small network of 5 PCs - PC-1 - PC-5. Each has its own IP address assigned and you want PC-1 to ping PC-4. When you ping, PC-1, first sends an ARP broadcast message. This message basically asks what the MAC address of x IP address is. In this case, it is asking for PC-4's MAC address. The broadcast message arrives at the switch. As I mentioned, the layer 2 switch doesn't understand IP addresses, but it looks at the destination MAC address. Broadcast frames are FF-FF-FF-FF-FF-FF. This tells the switch to forward that frame to all ports. So PC-2,PC-3, PC-4, and PC-5 all receive that broadcast frame. All computers except for PC-4 drop this broadcast. PC-4 responds to PC--1 with its MAC address. PC-1 learns this MAC address and can then send the ping message to PC-4.
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  99.  @brainoverload6288  You pretty much answered your question: Port forwarding. Port forwarding is used to forward ports, as the name implies from an external network to a device inside a network. In other words, if you have a web server in your home network, you can only access its webpages on devices inside of your home network. And if you want to access that web server from outside the network, you have to forward the necessary port(s) (80 for HTTP and 443 for HTTPS). So when you try accessing the web server from outside your network, your request arrives at your router. The router then forwards that HTTP request to the specified port and host inside of your network. In this case, it sends the HTTP request to your web server at port 80.
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  100. The switch has a CAM table. In short, when you plug in a device to the switch, the switch learns that device's MAC address and stores it in the CAM table as well as what port on the switch its plugged into. When the switch has a data frame to send, it looks in its CAM table to figure out what port to send the frame to.
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  101. It downloaded just fine for me. Have you tried using a different web browser?
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  102. Yes you would just need the MAC address. In practice, we primarily use IP addresses to send data to other computers even within the same network.
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  103. I think he goes over that in the next video. But you have to remember that when a device sends a packet, it works through the OSI model. At layer 3, you have the IP addresses. At Layer 2, you have MAC addresses. So when the PC sends a packet of data, the switch receives it. But it only cares about the layer 2 information, like the source and destination MAC addresses. When it gets the frame, it looks at that data and knows to send the packet to the port where that destination MAC address is on.
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  104. Yes. He pinged at layer 3, but notice when he clicks on the purple envelope. That window that opens shows information about the data that was sent, including the destination MAC address. So yes, the switch doesn't understand IP addresses. However, it will still receive the frame and look at the source and destination MAC addresses and send the frame to the correct port.
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  105. He goes over that in the next parts. In short, its called ARP - Address Resolution Protocol. ARP maps MAC addresses to IP addresses. Say you have a network of 5 PCs (PC-1 - PC-5). You ping PC-5's IP via PC-1. 1 needs 5's MAC address, but it doesn't know it. PC-1 will send an ARP message. This consists of a broadcast message at layer 2. The switch receives this broadcast message. It basically asks "What is the MAC address of the device with X IP?" Where "X IP" is PC-5's IP address. Since this is a broadcast frame, the switch forwards the frame to all switch ports. However, all devices (except PC-5) will drop the frame since they aren't the intended recipient. Only PC-5 will accept it and respond to PC-1 with its MAC address. PC-1 receives this response and will store the IP and MAC address in its ARP cache. After PC-1 stores PC-5's MAC address, it will send the ping packet. It now knows 5's MAC address and will send it only to that MAC address. PC-5 will receive this ping packet and respond accordingly. The network software of computer systems allow them to respond to pings and other network requests even if there is no router.
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  106. Nah. network hubs are not efficient. The way they work is that when a computer sends a packet of data to the hub, it will forward that packet to all ports. Switches only forward the frame to the respective switch port. In large networks, it would be extremely inefficient for all hub ports to receive all data even if it isn't for the intended device. That's why hubs are largely obsolete in modern computer networks.
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  107.  @bikinglikebecker  I still don't understand your thought process. If you're referring to shared network folders, then that's a thing that's been possible for years. There's no 'hub' involved.
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  108. You're supposed to make an account with Cisco Netacad. Otherwise it won't let you use the software. Its a dumb requirement IMO.
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  109. No. Intel and AMD CPUs use the x86_64 architecture. Pretty much any modern program designed for x86-64 CPUs will work on modern CPUs.
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  110. You download the packet tracer file he has linked in the description.
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  111. Well its unlikely 2 devices will have the same MAC address on the same network. If it does happen, then neither device will work correctly on the network. Again, this is not likely to happen. Same thing with an IP address. If you have 2 devices on the same network with the same IP addresses neither will work correctly. It won't damage anything, but they won't work. You'll need to remedy those situations.
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  112. It starts with your computer. When your PC wants to send a packet to another device, it needs both the destination IP and MAC addresses. If it doesn't know the MAC address, your PC will first a broadcast frame. When the switch receives the broadcast frame, it will send it out to all devices connected to its ports. The frame basically asks "What is the MAC address of the device with this IP address?". All devices on the switch will receive the frame, but all will drop it except for the intended recipient. The recipient will then respond to your PC with its MAC address.
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  113. That's because the PC initially doesn't know the MAC address of the destination computer.
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  114. A L2 switch has no concept of IP addresses or any other OSI layer concept for that matter. It starts with your computer. When your PC wants to send a packet to another device, it needs both the destination IP and MAC addresses. If it doesn't know the MAC address, your PC will first send a broadcast frame. When the switch receives the broadcast frame, it will send it out to all devices connected to its ports. The frame basically asks "What is the MAC address of the device with this IP address?". All devices on the switch will receive the frame, but all will drop it except for the intended recipient. The recipient will then respond to your PC with its MAC address. Your PC will learn this address and then will be able to directly communicate with that device.
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  115. Because there are 2 different networks he shows.
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  116. Make sure you scroll over to the right to see the network diagram.
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  117. I think he goes over in the next video. In short, when the 1st PC sends data to the 2nd PC, PC 1 adds the MAC address of the 2nd device in the destination MAC address. However, if PC1 doesn't know PC2's MAC address, PC1 first sends a broadcast frame. Basically a broadcast frame is a message that's sent to all devices on the network. The broadcast frame basically asks "What is the MAC address of the device with this IP address?". Since its a broadcast, all devices on the network receive it, but all devices will ignore that frame except for the intended device. PC2 will then respond to PC 1 with its (PC2) MAC address. From that point, PC1 will add PC2's MAC address in the destination mac address whenever it sends it data.
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  118. Watch the next video. He goes over that.
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